cmd/link/internal: add support for internal linking on loong64

cmd/link/internal: add support for internal linking on loong64

Change-Id: Ic0d36f27481ac707d04aaf7001f26061e510dd8f
Reviewed-on: https://go-review.googlesource.com/c/go/+/533716
Reviewed-by: Qiqi Huang <huangqiqi@loongson.cn>
Reviewed-by: sophie zhao <zhaoxiaolin@loongson.cn>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>